Commercial concrete is a mixture of cement, sand, and stone aggregate that, after the addition of water, slowly hardens together into a rigid structure. Stresses within concrete structures are typically of three primary types: compressive (where particles are crushed together), tensile (where particles are pulled apart), and shear (where one section of a structure is pressured to slide upon an adjacent section).
Unreinforced concrete structures often have good resistance to compressive stresses. However, any significant tensile stresses tend to cause undesirable cracking and separation since concrete is relatively weak in tension. To address this problem, concrete structures are typically reinforced by embedding in place within the rigid structures smaller solid members made of material(s) with high strength in tension. Typically, the smaller members include round steel bars with roughened surfaces, often called “reinforcing steel,” “reinforcing bar,” or “rebar.” Reinforced concrete structures are available commercially in many shapes and sizes, such as slabs, beams, footings, and flat foundations.
Unfortunately, reinforced concrete structures are still highly susceptible to shear forces that create diagonal tensile stresses, which can result in structural failures. Cracking and/or breaking caused by shear forces tend to propagate throughout the stressed zone of a concrete structure. This problem is especially acute in concrete slabs or other supported structures that are supported by columns or other supporting structures. In these types of situations, a slab is subject to a concentration of stresses in a zone near a column, where the column tends to “punch” upward through the slab. The resulting shear forces create diagonal tensile stresses within the supported structure.
For this reason, supported structures are typically reinforced in the areas around columns or other supporting structures. This is done to prevent tensile failure, crack propagation, and consequent structural collapse. However, conventional approaches often provide reinforcement that helps restrain or minimize cracking or breaking only after the cracking or breaking has started. These conventional approaches are typically unable to prevent cracking or breaking from occurring in the first instance.